# Tagged Questions

Questions related to the perception and measurement of light (primarily in the visible range), its mathematical description, the reproduction of colors by different means, color combinations, etc. Please use the tag [electromagnetic-radiation] if you want to refer to the general form of light.

135 views

### Why can gold be drawn out finer than light?

The metal gold is extremely malleable. Gold is also ductile and one ounce can be drawn into 80 km (50 miles) of thin gold wire (5 microns diameter) to make electrical contacts and bonding wire. I ...
90 views

### What is the minimal size of the spec of dust I can see with naked eye?

When sun directly shines thru the window - I can see small specs of dusts in the air. All specs have different sizes. Assuming direct sun luminosity is 100kLux, spec is a perfect sphere, reflection ...
36 views

### What is a n-type doped solar cell?

I always thought a solar cell consists of two areas, a n-type and a p-type doped one. So what exactly is meant by n-type doped solar cells? Does it not have a p-type doped area? And how does it work ...
98 views

### Explanation for the spectrum of the sun?

My Question is, why exactely does the intensity vanish below 240 nm ? If i look at the plank's law, obviously the intensity for $\lambda \rightarrow 0$ and $\lambda \rightarrow \infty$ will vanish, ...
384 views

### Fringe width and spacing and number of slits in diffraction experiments

In a single slit experiment, the fringes are not equally spaced and aren’t of equal widths—the central maximum is the widest, the secondary maxima grow narrower and narrower outward, and the minima ...
73 views

### How to transmit light ideally through not parallel tiny holes within a metal case?

I currently try to transmit light through a tiny hole of one side of a metal case in order to receive the light on the other side of the case. The tiny holes are not parallel (see image 2). Using ...
26 views

### can light bounce off another light? [duplicate]

If light is a wave and a particle (wave particle duality), is it possible for light to bounce off another light since light bounces of another matter(particle)?
62 views

### Light Spectrum - Sum of Waves or Collection of Waves

I am wondering about the spectrum of light that is often shown pictorially as a distribution of power, say, from sunlight. My question is: does this indicate that each wave of light contains all of ...
876 views

### Why Does The Moon Apear White/Grayish and The Sun Yellow? [duplicate]

The Sun, as we all know, is white. Because our atmosphere scatters light the sun appears yellow to us hear on earth. So, why isn't the moon also yellow. Doesn't our atmosphere scatter its light. How ...
2k views

### Why we can't see light emitted from TV remote while a camera can?

If we try to see light emitted from tv remote we can see this. while if we try same in camera we are able to see this. Why?
89 views

### In Fermat's Principle of Least Time, how do we know that light is able to reach the end point? [duplicate]

From my understanding of Fermat's Principle, you decide a start point and an end point for a light ray to travel between, and the light 'chooses' whichever path takes the least time (or technically ...
64 views

### What happens when the frequency of light propagating through a solid equals the resonance frequency of the electrons in the atoms? [closed]

I was reading this article and the following questions came to my mind: During the propagation of light through a solid, the photons collide with the atom making the electrons vibrate. What happens ...
245 views

### Hydrogen Spectra using Hydrogen Gas Discharge Tube

I am doing an experiment for my lab work which include determination of value of Rydberg Constant using method of Interpolation. For this we first plot calibration curve for various wavalengths ...
5k views

### How do we see? Where do the photons disappear?

I know that the light is reflected from a object to my eyes, but I don't understand exactly how. The photons appear from the light source and disappear in my eye! Can someone explain the phenomenon of ...
79 views

### How to turn the light stronger than your strength in start

Imagine the following scenario: I have one lamp, and I would like to turn it stronger, like a strength of 2 lamps. Can I do it, passing the light (for example) through one crystal or a special glass?...
250 views

### Physics of color: why do visible colors absorb all colors except the color itself?

It's funny I cannot answer this question, but I really don't have a very good physical intuition for how color works. I know that sunlight and (say) light from lightbulb is a superposition of all ...
434 views

### What is the significance of wavelength when referring to light (in layman's terms)?

Without any equations or complex terminology, I simply want to understand in complete layman's terms what the significance of a single photon's wavelength is. People say that microwave radiation's ...
55 views

### Can a beam of light be modulated close to it's frequency?

I'm wondering if it would be possible to modulate a signal using photon pulses - where the frequency of the signal would be close to the frequency of the light. Also would it be possible to transmit ...
32 views

### How far do the propagation paths in QED go?

I am currently reading Feynman's popular book on QED "the strange theory of light and matter". I know classical optics quite well, know about Fresnel, Brewster angle and the like. I also am now used ...
158 views

### How do we know that the CMBR is the oldest light?

How do we know that the CMBR is the oldest light which we can see? Is it based just on the facts 1.that waves redshift with expanding space, and 2.predictions of the big bang theory; Or is there a way ...
78 views

### Optics of perceived shadows on LCD monitor

After changing my desktop wallpaper on my LED-lit LCD monitor to one with a dark corner, I started seeing shadows on where the clock widget is while looking sideways at the screen. These shadows move ...
116 views

### How does light focused through a lens create bokeh (blurry background)?

This question is relevant, though I don't think it quite answers the question. From a photography perspective, when you open the aperture wide (with a small f-number) you get a very shallow depth of ...
334 views

### What causes the sharp borderline at the bottom of northern lights?

The northern lights are caused by cosmic charged particles interacting with the earth's upper atmoshphere. The particles can be trapped by the Lorentz force, so that we can see them where the magnetic ...
5k views

### Why does a moving fan seem transparent?

We all know when fan starts moving faster, we cannot see its blades. Why is this? First I assumed persistence of vision may be the reason. But that can happen with blade also right? Image of blade ...
1k views

### Is heat always associated with Light?

I have found that light always produces heat. The only cases I think heat is absent with light is Fluorescence and Phosphorescence (maybe because they emit low energy but maybe the heat is still ...
28 views

### Computing color and brightness of a hot material

Every blackbody color calculator I've managed to find only calculates hue and saturation; they completely ignore brightness, which severely limits their usefulness if you're trying to model the actual ...
374 views

### Why does shining a laser into an iPhone camera create these shapes?

When I shine a laser light into an iPhone 6 camera I get these weird shapes: The shapes are in no way in the background behind the laser. What causes these to appear? I know about typical lense ...
128 views

### How can the Hubble telescope see the light from galaxies that are millions of light years distant?

The Hubble Space Telescope is in the news every now and then. How can it photograph galaxies that are millions of light years from Earth? We can understand that light comes from galaxy and Hubble "...
84 views

### Do photons experience every moment in time and position in space simultaneously? [duplicate]

Would it be more correct to say that a photon, traveling at the speed of light, would experience all points in time simultaneously, and therefore be everywhere at once? It might be just our ...
47 views

### can i convert the visible light into another form of electromagetic light form?

can I convert the visible light form into another form of electromagnetic light??actually I want to make a device which convert the objects which are visible to the human eye into invisible as a part ...
214 views

### UV absorption decrease with an increase in concentration

I am working on a project measuring the absorbance of a solution which contains surfactant and hard brine. The solution has a constant concentration of surfactant and varying concentration of hard ...
363 views

### What range of light wavelengths can a typical mirror reflect?

A typical mirror is capable of reflecting the full spectrum of visible light. Can it also reflect other wavelengths both longer and shorter? What is the range?
166 views

### What is really a light ray? [duplicate]

I've been studying geometric optics and I'm still a little confused with this idea of light ray. In the book I'm studying everything is being done starting from Fermat's principle which states that ...
71 views

### Is it true that light has a lot of energy but cannot exert force [closed]

When a photon hits a mirror it is reflected ,it does not affect the mirror.But why when light has infinite energy?
68 views

### Why can i see LCD screen trough my linearly polarized glasses

I have a Samsung Galaxy Pocket Neo GT-S5310, it uses an LCD screen. Wikipedia says that all LCD's emit a vertically polarized light However even if I turn my glasses 90 degrees, i can still see the ...
91 views

### Colour changing material/ink

i am not sure if this is the right place to ask but is it possible for me to make an ink or material that changes colour when electricity goes through it at home? (as much colours as possible and low ...
283 views

### Why photons reflect off glass?

Why photon reflects and refracts through glass? Some photons pass through glass and some reflects.I know this is due to energy levels of electrons of glass, an incoming photon is unable to excite the ...
133 views

### Could you view yourself in high gravity situations?

I'm trying to understand what effects gravity can have on light. First of all, I don't understand how gravity can even affect it, since it doesn't have mass, right? That is probably a separate ...
65 views

### Would an ordinary or fluorescent lightbulb generate electricity when exposed to light?

I was wondering whether the physic laws or the nature in which lightbulbs are constructed would allow for lightbulb to generate electricity when subjected to strong (intensive and concentrated) light.....
353 views

### What is the most common photon wavelength in our observable universe (not including the Sun)?

Ignoring the Sun, what is the most common wavelength of a photon that is received by us on average? (I am not asking what is the average wavelength, but rather what is the most common wavelength ...
5k views

### Where does light go after it enters a black hole?

Nothing passes through a black hole. Where do things go then? If light enters a black hole, what happens to it? Do things go to a white hole and resume in another universe?
34 views

### Can colour be synthesized from frequency?

Given the frequency of a mechanical vibration in the audible range, one can synthesize the sound on a computer. For example, I ask "what does 440Hz sound like?" and I can listen to this frequency as ...
23 views

### Would it be ok to say that not all light travels at the same speed when you consider its own perspective? [duplicate]

The reason I am asking is because higher energy would cause greater gravitational time dilation. Therefore I would expect, from the perspective of a radio wave, a gamma ray having more energy would ...
733 views

### Question about lens maker's formula

I am trying to follow the derivation of lens maker's formula from the textbook "University Physics", p.1133 (https://books.google.com.hk/books?id=nQZyAgAAQBAJ&pg=PA1133#v=onepage&q&f=false)...
20 views

### How much energy will fall into the eye given luminosity of display

The smart-glasses have tiny display. The manufacturer says the display has luminosity of $2000 cd/m^2$. The area of display is around $0.0002 m^2$. The reference smartphone display has luminosity of \$...
17 views

### Transparency of atoms [duplicate]

Which is the specificity of the atoms which allow to pass the light, from which mass, from which composition of the core or the number of atoms the transparency falls. Electrons can collide with the ...
66 views

### Why conductors don't scatter light?

Air molecules can be oscillated by E field and re-radiate EM waves in different directions. However, if light is shined to a conductor the E field oscillate the free charges but the effect is to ...
117 views

### How do EM waves travel in a vacuum? [duplicate]

Apart from that electric and magnetic field variation thing, is there any other explanation? Can photons simply pass through vacuum?